Impact of operational conditions on development of the hydrogen-producing microbial consortium in an AnSBBR from cassava wastewater rich in lactic acid

Abstract

Biohydrogen production from cassava starch wastewater was evaluated in anaerobic sequencing batch biofilm reactor (AnSBBR) using different inoculum (mixed cultures from naturally fermented wastewater and anaerobic sludge thermally treated) and feeding strategies (batch and fed-batch). The highest hydrogen productivity (2.4 LH 2 L −1 d −1 ) and yield (11.7 molH 2 kg −1 Carbohydrates) were verified in low and intermediate organic load rates (12 and 14 g L −1 d −1 ) and longer cycle time (4 h), respectively. The productivity was favored by fed-batch strategy, and yield by batch. The hydrogen production was verified in both inoculum sources. However, in the assays inoculated from naturally fermented wastewater, with higher organic load rate (18 g L −1 d −1 ) and intermediate cycle time (3 h) no hydrogen was observed, regardless the feeding strategy, indicating that the inhibitory effects of the indigenous microorganisms present in cassava starch wastewater were more expressive in these conditions. The operational conditions applied to hydrogen production in AnSBBR from cassava starch wastewater may influence the microflora development in the reactor. In this study three possible scenarios were verified: hydrogen-producing bacteria (HPB) growth; hydrogen-producing bacteria inhibition or coexistence between ones and lactic acid bacteria (LAB), which are autochthones of this wastewater. © 2018 Hydrogen Energy Publications LLC